| Summary: | The goal of this thesis is to set up a methodology to establish a relationship between pulp properties, namely morphological and physical, and paper properties, specifically structural, optical and strength, with the operating variables of refining and the physical and chemical properties of the raw material. The goal is to contribute to the analysis of the beatability of chemical pulps for paper production. The beatings took place in a laboratory Valley beater, and the studied variables were the charge on the roll, the rotor speed of rotation and the specific applied energy. For its feasibility, one fitted the following adaptations to the Valley: a rotor speed of rotation variation controller, a sensor to measure the distance between rotor and stator and an electrical power consumption meter. The effects for three different bleached Kraft pulps were studied, one being pine and the others Portuguese eucalyptus and birch. At the fibre level, its morphology was analysed by image analysis, such as the average fibre length and distribution, its width, coarseness, curl, kinks, fibrillation and fines proportion; the intrinsic fibre resistance was evaluated, such as its water retention value and wet flexibility. At the paper level, one measured its density, tensile strength, burst strength, tear strength, brightness, opacity and its scattering and absorption coefficients. One implemented methodologies to evaluate the relative bonded area and the bond strength in the paper structure using optical and mechanical methods. The hydromechanics of the beating was analysed for the three pulps. So the beating effects on the specific edge load was studied, the normal and tangential forces were evaluated, the pulp apparent viscosity evolution during refining was determined, the distance between rotor and stator was measured and also the energetic efficiency was quantified. One obtained relationships between the apparent viscosity and the rotor-stator gap, and another between the first one and the rate of shear. One explored the experimental results in order to develop control relationships for the pulp properties to paper production. One essayed an optimization of the refining conditions for each pulp for specific types of industrial papers, namely in terms of paper properties and the energy consumption in the Valley beater. The pulp suspension presents rheofluidificant behaviour and the apparent viscosity diminishes along the refining. The different pulps reveal different rheological behaviour, which leads to the inference that from the hydrodynamical point of view one should treat pulps with different morphological characteristics separately. The obtained adjustment equations for the different studied properties permit the comparison between the pulps and the study of the effects of the operating conditions. As expected, the pine revealed the best strength performance, the eucalyptus showed the best optical properties, and the birch showed a better mechanical performance relatively to the other hardwood. In what concerns the analysis of the operating conditions, one verified that the rotor speed of rotation has a major influence on the pulp and paper properties. One also inferred that the birch reveals an opposite behaviour comparatively to the pine and the eucalyptus, from the standpoint of the sped of rotation and the specific edge load.
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